1. Technical Field
This invention relates generally to a bicycle having a rotating force transmitting mechanism with an oscillating fulcrum point. More particularly, the invention relates to the bicycle wherein a crank lever is arranged between a sprocket and a pedal lever to transmit force applied to the pedal lever to the sprocket and the oscillating fulcrum point of the pedal lever is slidable and wherein a sliding part is provided with a dust-resistant means to prevent dust and the like from being entered therein and to remove the dust, if entered, therefrom.
2. Related Art
The conventional bicycle is operated such that the crank-like pedals fixed at both sides of a shaft of the sprocket with a phase difference of 180xc2x0 are stepped on by a rider. The pedal lever is rotated around the shaft of the sprocket to attain rotating force of the sprocket and this rotating force of the sprocket is transmitted to the rear wheel through the chain.
However, in recent development of the bicycle, there has been proposed to provide a bicycle having a driving force generating device with an oscillating fulcrum point, whereby the rider is less fatigued with a riding as compared with the conventional bicycle, and desired propulsion force can be attained.
FIG. 1 schematically shows a configuration of the related art bicycle having the driving force generating device with an oscillating fulcrum point. In FIG. 1, a bicycle 60 having the rotating force transmitting mechanism with the oscillating fulcrum point is constructed such that a front wheel 61 acting as a moving wheel and a rear wheel 62 acting as a driving wheel are attached to a pair of delta-shaped frames 63, 64; a handle 65 is attached to a front frame 63; and a saddle 66 is fixed to a rear frame 64.
A wheel shaft 61a of the front wheel 61 is rotatably attached to extremity ends of a fork section 67a formed at the lower part of a handle frame 67. Connecting portion 63a constituting the front frame 63 is extended longitudinally in a reverse direction to a direction that the bicycle is headed, from a holding part 63c holding the handle frame 67 rotatably.
Connecting portion 63b also constituting the front frame 63 is extended in a rearward and downwardly slanting direction from the holding part 63c. The extremity ends of these connecting portions 63a, 63b are connected to a saddle frame 64c. The saddle frame 64c constitutes the rear frame 64 and is substantially in parallel with the handle frame 67. The saddle 66 is fixed to this saddle frame 64c. 
Respective connecting portions 64a and 64b constituting the rear frame 64 are extended from the connecting portions 63a and 63b. The extremity ends of these connecting portions 64a, 64b are connected to each other to hold the wheel shaft 62a of the rear wheel 62 horizontally. Respective gears 75R and 75L (not shown) are attached and fixed to both ends of the wheel shaft 62a. FIG. 1 illustrates the configuration of the bicycle in which only the gear 75R at the right side toward a direction which a bicycle is headed, is shown.
The gear 75R is engaged with a gear train, not shown, and the crank 76R is fixed for transmitting its rotating force to the gear 75R through the gear train. A crank pin 77R is fixed to a position displaced in respect to a shaft 78R of the crank 76R. A right side pedal lever 72R holds rotatably the crank pin 77R so that the crank 76R may be rotated with the crank pin 77R.
The right side pedal lever 72R attaches a right side pedal 71R rotatably at a front end thereof. The pedal lever 72R attaches a roller 73R pivotally at a rear end thereof. The roller 73R is freely slid in a sliding part 74R formed near the wheel shaft 62a. 
The pedal lever 72R acts as a lever oscillating upwards and downwards with the roller 73R pivoted at the pedal lever 72R being applied as a fulcrum point.
When the rider steps on the pedal 71R acting as a force applying point, the pedal 71R is moved in a counter-clockwise direction along a locus S approximating to a flat ellipse shape. At the same time, the pedal lever 72R is moved upwards and downwards in a predetermined angle with the roller 73R being applied as a fulcrum point.
This motion allows the crank 76R to rotate in a counter-clockwise direction around the shaft 78R through the crank pin 77R acting as a lever force applying point of the pedal lever 72a. At this time, the roller 73R acting as a fulcrum point for the pedal lever 72R is slid (moved) laterally within the sliding part 74R.
While the crank 76R is rotated, the rotating force of the crank 76R is transmitted to the gear 75R through the gear train. A clockwise directional rotation of the gear 75R causes the wheel shaft 62a of the rear wheel 62 to rotate for obtaining propulsion force of the bicycle 60. The propulsion force enables the bicycle 60 to run.
Since a left-side pedal lever 72L (not shown) is provided with the same driving force transmitting mechanism as that of the right side pedal lever 72R described above, a rider steps on the pedals 71R and 71L (not shown) alternatively by his (her) right and left feet to obtain propulsion force for the bicycle 60. Thereby, the bicycle 60 may run.
In the configuration of the aforesaid bicycle 60, a sliding part 74R formed on an end of the connecting portion 64b, is opened. Therefore, the foreign particles such as dust are prone to enter the sliding part 74R when the bicycle 60 is set outside or it is fallen to the ground. Entering of the foreign particles causes the sliding part of bicycle 60 to be injured. The foreign particles in the sliding part cause a faulty locus Q of motion of the pedal of the bicycle 60.
The object of the present invention is to provide a bicycle in which a sliding part is provided with a dust-resistant means to keep foreign particles such as dust from entering the sliding part and to remove the foreign particles, if entered, therefrom so that a smooth locus Q of motion of the pedal can be assured.
In carrying out the invention in one preferred mode, we provide a bicycle comprising a frame constituting a chassis, a steering means attached to the frame, a seat means for seating a rider attached to the frame, a pair of moving wheels rotatably arranged at the frame on a front side and a rear side thereof, said rear moving wheel acting as a driving wheel, a sprocket arranged near a bottom bracket point in the frame, driving force transmitting means for transmitting rotating force of the sprocket to the rear moving wheel, a pair of pedal levers having a phase difference of 180xc2x0 with respect to each other to oscillate alternatively up and down, a crank lever arranged between the sprocket and the pedal lever so as to transmit force of the pedal lever to the sprocket, a sliding part for acting as an oscillating fulcrum point of the pedal lever and dust-resistant means provided with the sliding part.
A sliding pin arranged at one end of the pedal lever is slid within the sliding part while the pedal lever is oscillated. The force accompanied by the oscillation of the pedal lever is transmitted to the rear wheel through the sprocket.
In the present invention, force applied to the pedal by the rider is transmitted to the rear wheel under utilization of the crank lever, the sprocket and the chain. The force of the pedal lever is transmitted to the sprocket through the crank lever. The oscillating fulcrum point of the pedal lever is moved, not fixed, laterally in the sliding part.
As the pedal lever is stepped on by the rider, the oscillating fulcrum point is moved laterally, so that even when the locus of motion of the pedal is different in reference to the first half period (from the upper dead center to the lower dead center) and the second half period (from the lower dead center to the upper lower center), a smooth motion of the pedal is obtained.
The sliding part is provided with dust-resistant means such as a cover to keep the smooth motion of the pedal without a hitch. The dust-resistant means keeps foreign particles such as dust from entering the sliding part and removes the foreign particles, if entered, from the sliding part. If the foreign particles are prone to enter the sliding part of bicycle 60 when the bicycle 60 is set outside or it is fallen to the ground, the sliding part is not injured by the foreign particles and a faulty locus Q of motion of the pedal of the bicycle 60 does not occur.
A further understanding of the nature and advantages of the invention may be realized by reference to the following portion of the specification and drawings.